Publish symbols to nuget and symbol server

[jasongin]

We need to publish symbols to NuGet and the Microsoft public symbols server.

NuGet symbol publishing is helpful for NuGet-packaged binaries, but we also publish some binaries via npm packages. For those, the Microsoft symbol server is probably the best approach.

[jasongin]

Nuget symbol packages (.snupkg) are published to nuget.org starting with version 0.8.4.

We still need to publish symbols for the binaries that are not published in nuget packages.